Assembly comprising a bicycle fork and a headset on a bicycle frame and fork for one such assembly

ABSTRACT

The invention relates to an assembly comprising a bicycle fork ( 1 ) and a headset (J) on a steering column ( 2 ) of a bicycle frame. According to the invention, the fork is solidly connected to a pivot ( 3 ) which extends ( 3   a ) beyond the end of the steering column, opposite that comprising the fork, such that a handlebar stem can be fixed thereto using the external screw thread of the pivot. The aforementioned headset (J) comprises a lower bearing ( 7 ) and an upper bearing ( 8 ) and an adjustment means (M) is provided for the axial clamping of said headset. Moreover, in the area at the end of the steering column opposite that comprising the fork, the outer surface of the pivot ( 3 ) contains a zone (B) which is equipped with first connecting means ( 13 ), while the above-mentioned pivot extension (3 a ), which is disposed at the end opposite that comprising the fork ( 1 ), has no such connecting means. The invention further comprises a bushing ( 15 ) which is equipped with second connecting means ( 16 ), complementary to those of the pivot, and which is used to adjust the axial clamping of the headset.

The invention relates to an assembly of a bicycle fork and of a steeringheadset on a steering column of a bicycle frame, the fork being securedto a pivot which is extended beyond the end of the steering columnfurthest from the fork to allow the attachment of a handlebar byexternally clamping the pivot, the steering headset comprising a lowerbearing and an upper bearing which are arranged between the pivot andthe column, while an adjusting means for adjusting the axial clamping ofthe steering headset is provided.

An assembly of this kind, known as a “headset” is based on the principleof holding the bearing/fork assembly together by immobilizing thehandlebar on the fork pivot. An example is disclosed in FR 2 815 928 inthe name of the same Applicant Company.

This principle has advantages in terms of the rigidity of theconnection, the lightness of weight, the use of new materials,particularly composites, by comparison with the solution which consistedin introducing a handlebar stem inside the pivot and in immobilizing thestem in the pivot using an expansion device. However, these assembliesare awkward to achieve, particularly as far as adjusting the steeringheadset is concerned.

Specifically, in known assemblies of the headset type, in order toadjust the axial clamping of the steering headset, use is made of anaxial thrust from a sleeve secured to the handlebar. Now, the positionof the handlebar and of its sleeve, in the axial direction of the pivot,depends on the cyclist's build and desires; this position cannottherefore be pre-set at the factory without the cyclist who is going touse the bicycle being present. It is therefore down to the specialistretailer to set it up to suit the user. The retailer has therefore toadjust the clamping of the steering headset, having assembled thecomponents and fitted the handlebar.

This relatively awkward operation is often very temporary because theuser may wish to alter his position on the bicycle and change thehandlebar settings. Each action on the handlebar has the effect ofaltering the settings of the steering headset in known assemblies, whichmeans that the steering headset has to be readjusted.

It is an object of the invention, above all, to provide an assembly ofthe aforementioned kind in which the steering headset can be set at thefactory independently of the position of the handlebar, so that theretailer does not have to work on the steering headset when setting upthe bicycle. Furthermore, it is desirable for the cyclist who is goingto use the bicycle to be able to adjust the handlebar without alteringthe settings of the steering headset.

According to the invention, an assembly of a bicycle fork and a steeringheadset on a steering column of a bicycle frame, of the kind definedhereinabove, is characterized in that:

-   -   the pivot comprises, in the region of the end of the steering        column furthest from the fork, on its exterior surface, a zone        equipped with first connecting means, the extension of the pivot        on the opposite side to the fork having no such connecting        means,    -   and a bushing equipped with second connecting means,        complementing those of the pivot, is provided to allow the axial        clamping of the steering headset to be adjusted by collaboration        with the first connecting means.

As a preference, the zone of the pivot equipped with the firstconnecting means consists of a ring of determined length slipped aroundthe pivot and fixed to the latter. The ring may have an external screwthread comprising the first connecting means.

The second connecting means may be formed by an internal screw threadprovided on the bushing and the conjugate of that of the ring.

The ring may be fixed to the pivot by bonding. The pivot may be made ofcomposite and the attached ring may be made of metal.

The bushing is advantageously formed of a steering cup. Arotation-proofing brake may be provided between the bushing and thepivot. This brake may consist of an O-ring.

The length of the threaded ring may be about 1 cm.

As an alternative, the axial length of the threaded ring, or moregenerally of the zone equipped with the first connecting means, issufficient to allow the steering headset to be clamped and adjusted withdifferent heights of steering column.

The invention also relates to a fork for such an assembly, this forkbeing secured to a pivot which is extended to allow a handlebar to beattached by external clamping of the pivot, and characterized in thatthe pivot comprises, in a region furthest from the fork, on its exteriorsurface, a zone equipped with first connecting means, the extension ofthe pivot on the opposite side to the fork having no such connectingmeans. The zone of the pivot equipped with the first connecting meansadvantageously consists of a ring of determined length slipped aroundthe pivot and fixed to the latter.

Apart from the provisions set out hereinabove, the invention consists ina certain number of other provisions which will be dealt with moreexplicitly hereinbelow with regard to an exemplary embodiment describedin detail with reference to the attached drawings, but which is not inany way limiting.

In these drawings:

FIG. 1 is a perspective view with partial cutaway of a fork-steeringheadset assembly on a bicycle frame according to the invention;

FIG. 2 is an exploded perspective view of the parts of the assembly ofFIG. 1,

FIG. 3 is a vertical section in perspective on a larger scale of thesteering cup, and

FIG. 4 shows, in perspective, the fork and the pivot both equipped withthe steering cup.

Reference is made to FIG. 1 which shows an assembly A of a bicycle fork1 and of a steering headset J on a steering column 2 of a bicycle frameC.

The fork 1 is secured to a pivot 3 which is extended at 3 a beyond theend of the column 2 furthest from the fork 1, that is to say beyond theupper end of the column 2 in the case of a bicycle in the runningposition. The part 3 a of the pivot 3 allows the attachment of ahandlebar 4, depicted schematically and partially, which comprises atthe rear a sleeve 5 surrounding the pivot 3. The pivot 3 is cylindrical,generally of circular cross section, preferably with a diameter that isconstant in the axial direction, at least in the handlebar attachmentzone. The sleeve 5 is generally split at the rear along a generatrix andcomprises clamping means, particularly screws 6, to allow the handlebarto be immobilized on the pivot 3 by external clamping of the pivot 3.The pivot may comprise one or more internal stiffening partitions 3 b.

The steering headset J comprises a lower bearing 7 and an upper bearing8 both arranged between the pivot 3 and the column 2, and an adjustingmeans M for adjusting the axial clamping of the steering headset J.

The lower bearing 7 is internally centered on a bearing surface 9 of thepivot and is arranged axially between seat 10 machined at the base ofthe steering column and a shoulder 11 of the fork 1. The upper bearing 8is arranged between a seat 12 provided at the upper end of the column 2and the means M for axially clamping the steering headset J.

The axial clamping of the steering headset J, and more precisely of thebearings 7 and 8, is adjusted by altering the dimension E whichcorresponds to the distance between the shoulder 11 and the bearingsurface via which the means M bears against the upper bearing 8.

In the hitherto known devices, the axial clamping of the headset J isobtained by bearing, if necessary with the interposition of shims,against the lower part of the sleeve 5 when the handlebar has beenadjusted. A change in the position of the sleeve 5 therefore alters theaxial clamping of the steering headset J.

According to the invention, the pivot 3 comprises, in the region of theend of the column 2 furthest from the fork 1, on its exterior surface, azone B equipped with first connecting means advantageously consisting ofa screw thread 13.

As a preference, the zone B consists of a ring 14 the exterior surfaceof which is equipped with the screw thread 13 and the cylindricalinterior surface of which is smooth. The inside diameter of the ring 14is equal to the outside diameter of the pivot 3. The ring 14 is slippedaround the pivot 3 and fixed to the latter, particularly by bonding.

The axial length h of the ring 14 may be about 1 cm, which is enough toadjust the clamping to correspond to a determined height of column 2.However, a greater length h may be anticipated and this would allowaxial adjustment with steering columns 2 of different heightscorresponding to frames C of different sizes.

The extension 3 a of the pivot on the opposite side to the fork 1comprises a plain exterior surface with no screw thread.

The pivot 3 may be made of a composite based on carbon fiber resin,while the ring 14 is made of metal. Of course, the pivot 3 may also bemade of metal, particularly steel, or of aluminum or of titanium.

A bushing 15, equipped with second connecting means, advantageouslyconsisting of a screw thread 16 that is the conjugate of the screwthread 13 of the pivot is provided to allow the axial clamping of thesteering headset J to be adjusted by turning the bushing 15 relative tothe pivot 3.

The bushing 15 consists of a steering cup 17, clearly visible in FIG. 3,comprising a sleeve 18 with the internal screw thread 16 and a skirt 18separated radially from the sleeve 18 and determining an annular housing20 for the bearing 8. The skirt 19 is connected to the upper part of thecup 17 by a frustoconical wall 21.

The bearing 8 comprises a lower ring 8 a resting against the seat 12 andan upper ring 8 b having, radially toward the inside, a frustoconicalsurface 22 widening towards the top, coming to rest against afrustoconical shoulder 23 provided on the sleeve 18. Rolling elements,for example balls, not visible, are provided between the rings 8 a and 8b.

The upper part of the cup 17 forms a collar which, on the inside, has anannular groove in which an elastomer O-ring 24, designed to rubinternally against the surface of the pivot 3 and to slow the rotationof the cup 17 relative to the pivot 3 is housed. This example of arotation-braking means is non-limiting, it being possible for otherknown means to be envisaged.

That being the case, the assembly A is produced then the axial clampingof the steering headset is adjusted, as follows.

The threaded ring 14 is fixed, preferably by bonding, at a distance Lfrom the shoulder 11 of the top of the fork which depends on the size ofthe frame and, more precisely, on the height k of the column 2.

The lower bearing 7 is fitted around the pivot 3 and slid along, pastthe ring 14 until it comes to rest against the shoulder 11. If theoutside diameter of the ring 14 is greater than the inside diameter ofthe bearing 9, the latter would be placed on the shoulder 11 before thering 14 was bonded in place.

The pivot 3 is then engaged inside the column 2 until the bearing 9positions itself in the lower seat 10 of the column 2. The ring 14 isthen in the upper end region of the column 2, generally just above thisend, and the part 3 a of the pivot protrudes from the upper edge of thecolumn 2.

The upper bearing 8 is fitted around the pivot 3 and placed on the upperseat 12 of the column 2.

The steering cup 17 is then fitted around the pivot 3 and slid down tothe level of the ring 14. The cup 17 is turned to cause its interiorscrew thread 16 to collaborate with the screw thread 13 of the ring 14.The bearing 8 engaged in the housing 20 of the cup 17 comes to rest, viaits upper ring, against the shoulder 23.

Finally, the steering headset J is clamped to a predetermined torque.The frame-fork assembly is complete, with the clamping of the steeringheadset adjusted.

The frame-fork assembly can then be delivered to a specialist retailerwho will mount the handlebar 4 on the pivot 3 and adjust the handlebarto suit the build of the cyclist. When the handlebar 4 has been fixed inthe appropriate position, the part of the pivot 3 situated above thehandlebar will be eliminated by cutting the pivot off just above thehandlebar 4.

The adjustment of the handlebar is dissociated from the adjusting of thesteering headset. This results in a considerable simplification of thework to be done by the specialist retailer and better control of thequality of the steering since it is assembled and adjusted at thefactory.

The long-term stability of the adjustments made is improved.

To house the ring 14 without modifying the surrounding components allthat is required is the provision of a compact bearing 8 freeing upenough space to house the ring 14. It would, however, be possible to usea larger bearing 8 if the surrounding components were modified.

Although a screw thread is a simple and economical solution forproducing the conjugate connecting means 13 and 16, other equivalentsolutions such as a helical ramp and a radial peg collaborating with theramp may be envisaged.

1. An assembly comprising: a bicycle fork and a steering headset on asteering column of a bicycle frame; a pivot to which said fork issecured, wherein said pivot is extended beyond an end of the steeringcolumn furthest from the fork to allow the attachment of a handlebar byexternally clamping the pivot, and wherein said steering headsetcomprises a lower bearing and an upper bearing which are arrangedbetween said pivot and said steering column; a zone on an exteriorsurface of said pivot in a region of said end of the steering columnfurthest from the fork, wherein said zone includes first connectingmeans, and wherein said first connecting means comprises a ring slippedaround the pivot and fixed to the pivot by bonding, a pivot extensionextending from said zone in a direction away from said fork, whereinsaid pivot extension has no such first connecting means; and a bushingequipped with second connecting means complementing the first connectingmeans, wherein said bushing allows axial clamping of the steeringheadset to be adjusted by collaboration with the first connecting means.2. The assembly as claimed in claim 1, wherein the ring has an externalscrew thread.
 3. The assembly as claimed in claim 2, wherein secondconnecting means are formed by an internal screw thread provided on thebushing and the conjugate of that of the ring.
 4. The assembly asclaimed in claim 1, wherein the pivot is made of composite and the ringis made of metal.
 5. The assembly as claimed in claim 1, wherein thebushing is formed of a steering cup.
 6. The assembly as claimed in claim1, wherein a rotation-proofing brake is provided between the bushing andthe pivot.